Information Technology Reference
In-Depth Information
(transport layer). The TCP segment is placed in an IP packet (network layer) with a desti-
nation IP address of Host 2. The IP packet is placed in an Ethernet frame (data link layer),
which is converted into bits and sent onto the wire (physical layer).
TCP
Data
TCP
Data
Segment
Segment
Host 1
Packet
IP
TCP
Data
Packet
IP
TCP
Data
Host 2
802.3
IP
TCP
Data
802.3
IP
TCP
Data
Ethernet 1
Ethernet 2
Router 1
Serial Link
Router 2
IP
TCP
Data
IP
TCP
Data
HDLC
IP
TCP
Data
Destination IP
Destination IP
Figure C-4
Te l n e t E x a m p l e
When the frame arrives at Router 1, it converts the bits into a frame; removes the frame
headers (data link); checks the destination IP address (network); places a serial link header
on the packet, making it a serial frame; and forwards the frame to the serial link (data link),
which sends it as bits.
Router 2 receives the bits and converts them into a frame; removes the serial encapsulation
headers; checks the destination IP address (network); adds an Ethernet header to the
packet, making it a frame; and places the frame on Ethernet 2 (data link). Host 2 receives
bits (physical) from the Ethernet cable and converts the bits into a frame (data link). Then,
the IP protocol is examined and the packet data is forwarded to TCP, which checks the
segment number for errors and then forwards the segment to TCP port 23 (Telnet), which
is the application.
Numeric Conversion
This section focuses on the techniques for converting between decimal, binary, and hexa-
decimal numbers. Although the exam might not have a specific question about converting
a binary number to decimal, you need to know how to convert these numbers to do prob-
lems on the test. An IPv4 address could be shown as binary or in traditional dotted-
decimal format. MAC addresses and IPv6 addresses are represented in hexadecimal. Some
show
commands have output information in hexadecimal or binary formats.
Hexadecimal Numbers
The hexadecimal numeric system uses 16 digits instead of the 10 digits used by the deci-
mal system. Table C-1
